Render a "long" video (> 2 mins) in one step, without running out of memory
The short answer is: I was using an old version of Blender with a memory leak (thanks @3pointedit for pointing me in the right direction!).

I just installed 2.78c, and this version does not have the problem any more.

Just a note that as of March 2017, 2.76b was the latest version in the Linux Mint repository (and probably also in the Ubuntu repository).